An ink jet recording system is a recording system in which ink liquid droplets are jetted directly on a recording member from very fine nozzles and stuck to the recording member to print characters and images. This system not only has the advantage that the device to be used has a low noise and good operability but also has the advantage that coloration is easy and common paper can be used as recording members and is therefore widely used. As ink used for an ink jet printer, pigment type ink has been developed or used in recent years to improve water resistance and light fastness.
In pigment type ink, it is proposed, for example, that a polymer containing a polyethylene glycol (meth)acrylate monomer and α,β-ethylenic unsaturated carboxylic acid is added (JP-A 6-306317) and that a polymer dispersant comprising a polyethylene glycol (meth)acrylate monomer or a poly(trimethylene glycol) (meth)acrylate monomer (JP-A 2000-144031) is added in order to improve optical density.
It is also proposed that a macromer is compounded to improve light fastness and high optical density (WO-A 00/39226 and the equivalent EP-A 1059341). Moreover, for example, aqueous ink containing a water dispersion of polymer particles of a water-insoluble vinyl polymer of a monomer using a combination of an ethylene oxide and a propylene oxide which ink has excellent water resistance, rub fastness and dispersion stability is proposed (JP-A 2004-2662 and the equivalent EP-A 1323789).